Stereo camera

ABSTRACT

A stereo camera capable of photographing a stereo picture maintaining an optimum stereo effect. Right and left lens boards  42 R,  42 L of a stereo camera  41  are coupled to a camera body  46  via upper and lower two sets of parallel links  47 . Parallel grooves  45 L,  45 R are formed in the lateral direction in the inner portions of the lens boards  42 L,  42 R, and with which a circular eccentric cam  43  is engaged. When the shaft mounting the cam  43  is turned, the right and left lens boards  42 R and  42 L move in parallel describing circular loci, making it possible to automatically adjust the focal point as well as the distance between the optical axes of the lenses, which is important for accomplishing a stereo effect.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a stereo camera. Moreparticularly, the invention relates to a stereo camera which adjusts thedistance between the optical axes of two photographing lenses beinginterlocked to the operation for adjusting the focal point.

[0003] 2. Background of the Invention

[0004] In a stereo camera which takes two pieces of pictures at one timethrough a pair of right and left photographing lenses, the distancebetween the optical axes of the two photographing lenses has generallybeen fixed. In the stereo camera of this type in which the distancebetween the optical axes is fixed as shown in FIGS. 20(L) and 20(R) inan exaggerated manner, there develop non-overlapped regions (a-b, c-d)on the outer sides of the overlapped region (b-c) of the right and leftphotographed pictures L and R due to parallax of the two photographinglenses. As the distance to the subject becomes closer, furthermore, theposition of the image of the subject in the right and left photographedpictures undergo a displacement toward the directions to approach eachother.

[0005] The non-overlapped regions (a-b, c-d) are the portions where nostereo image is formed. When viewed by using a stereo slide viewer, thepicture frames of the slide mount are overlapped on the boundaries ofthe non-overlapped regions as shown in FIG. 21, which is offensive tosee. Besides, a stereo image of the subject at a distance closer than afocal distance appears in front of the stereo window (imaginary windowin which the right and left picture frames of the mount become inagreement and appear as one picture when the stereo slide is viewed in athree-dimensional manner), which is unnatural. The stereo slides thathave been proposed are accompanied by the above-mentioned defects.

[0006] In order to correct these defects, therefore, it has beenattempted to mask the non-overlapped regions (a-b, c-d) of the right andleft pictures by using a stereo slide mount having windows of a widthnarrower than the width of the pictures on the films, and to correct theperspective feeling by adjusting the pitch between the right and leftfilms. The above method, however, is accompanied by a difficulty fordetermining a proper masking amount and for determining the positions ofthe films relative to the windows of the mount in the transversedirection and, besides, involves large loss of picture due to masking.

[0007] The above-mentioned problems caused by a difference in the visualfield between the right and left photographing lenses can be solved bycorrecting the visual field by adjusting the distance between theoptical axes of the right and left photographing lenses. As the devicesfor adjusting the distance between the optical axes of the stereocamera, there have been known the one of the manually adjusting type foradjusting the distance between the optical axes irrespective of thefocal point-adjusting mechanism and the one of the automaticallyadjusting type for adjusting the distance between the optical axes beinginterlocked to a mechanism for adjusting the focal point. The device ofthe manually adjusting type is capable of adjusting the distance betweenthe optical axes of the lenses to an optimum value depending upon adistance to the main subject and upon a distance between the mainsubject and another subject, but requires cumbersome operation forseparately adjusting the focal point and the distance between theoptical axes. Though scenery and still life can be photographed withoutinterruption, this method lacks performance for quickly shootingpictures. Besides, the user may incorrectly set the distance between theoptical axes unless he is well accustomed to the operation and functionof the mechanism for adjusting the distance between the optical axes,which is never easy to handle. Accordingly, the automatic mechanism foradjusting the distance between the optical axes is more suited for astereo camera used by general public than the manual mechanism foradjusting the distance between the optical axes.

[0008] The conventional automatic mechanism for adjusting the distancebetween the optical axes has been so constituted that the vidual fieldsof the right and left photographing lenses are brought into agreement atall times at a focal distance and that the distance between the opticalaxes is automatically adjusted being interlocked to the adjustment ofthe focal point to obtain a constant effect for correcting the distancebetween the optical axes.

[0009] If it is presumed that the lens is a thin lens and,

[0010] focal distance of the lens - - - f

[0011] distance from the subject to a main

[0012] point of the lens - - - L

[0013] distance from the focal point of the

[0014] lens to the image-forming position - - - Δif

[0015] then,

Δif=f ²/(L−f)  (1)

[0016] and the distance from the main point of the lens to the surfaceof the film is given by f+Δif.

[0017]FIG. 22 illustrates loci of motion of main points of thephotographing lenses at the focal distance for bringing into agreementthe visual fields of the right and left photographing lenses. When thepitch between the right and left exposed pictures of the stereo camerais denoted by P, the shifting amount Sl of the right and left lenses forbringing into agreement the visual fields of the right and leftphotographing lenses at the focal distance is given by,

Sl=(P/2)×(f+Δif)/(L+f+Δif)  (2)

[0018] A table of FIG. 23 illustrates relationships between thedelivering amounts Δif of the lenses in the direction of the opticalaxes and the shifting amounts Sl in the direction at right angles withthe optical axes based upon the above-mentioned formula when a focaldistance of the lenses is 36 mm and the pitch P between the right andleft exposed pictures is 66 mm. When the right and left photographinglenses are moved toward the directions to approach each other by theshifting amount Sl accompanying a decrease in the distance L to thesubject that is focused, the loci of motion of main points of thephotographing lenses describe a loose curve, and the visual fields ofthe right and left photographing lenses at the focal distance arebrought into agreement at all times.

[0019] The conventional mechanism for automatically adjusting thedistance between the optical axes is so constituted that the main pointsof the photographing lenses move on loci given by the above-mentionedformula by using a cam, a guide and the like, and that the focal pointis adjusted being interlocked to the adjustment of the distance betweenthe optical axes. In practice, however, a satisfactory effect forcorrecting the distance between the optical axes is not obtained in manycases.

[0020] This problem is caused by the fact that all subjects in thepicture seldom exist at a focal distance and, in many cases, thesubjects are existing at various distances. For example, when a sceneryis to be photographed by bringing the focal point to infinity, somematerial bodies are in many cases photographed in front of the subjectat infinity. In taking a picture from a close distance, e.g., inshooting flowers in a flower garden from an upper tilted direction, thepicture includes flowers in front of the flowers at the central portionof the picture to where the focal point is adjusted. When a frontportrait is to be shot by adjusting the focal point to the eyes of ahuman model, the nose of the model is, then, located in front of thefocal distance.

[0021] In a stereo slide in which the subject that strongly affects thematching of the right and left images exists at a distance closer thanthe subject at the focal distance, the stereo image of the subject atthe closer distance is formed in front of the stereo windows and appearsunnatural. To correct this, it becomes necessary to mask the outer sideedges of the right and left pictures when the films are to be mounted inthe same manner as in the prior art and to correct the perspectivefeeling by adjusting the pitch for mounting the right and left films.Thus, the action of the conventional mechanism for automaticallyadjusting the distance between the optical axes is never perfect.

[0022] Therefore, a technical problem must be solved in order to providea stereo camera having a practicable function for adjusting the distancebetween the optical axes so that stereo pictures featuring an optimumstereo effect can be easily shot by anybody. The object of the presentinvention is to solve this problem.

SUMMARY OF THE INVENTION

[0023] The present invention is proposed in order to achieve theabove-mentioned object, and provides a stereo camera provided with amechanism for automatically adjusting the distance between the opticalaxes, in which two photographing lenses are mounted on independent lensboards, the distance between the right and left lens boards is changedbeing interlocked to the back-and-forth motion of the lens boardsaccompanying the operation for adjusting the focal point, and thedistance between the optical axes of the two photographing lenses iscorrected depending upon the focal distance, wherein the loci of motionof the two photographing lenses are right-and-left symmetrical straightlines connecting the positions at where the distance between the opticalaxes of the two photographing lenses at a position for adjusting thefocal point to infinity is narrower than a pitch between the right andleft exposed pictures or, preferably, connecting the positions within arange of distance between the optical axes in which the visual fields ofthe two photographing lenses are brought into agreement at a distance of2 to 3 meters in front of the main points of the photographing lensesalong the optical axes, to the positions of the distance between theoptical axes at where the visual fields of the two photographing lensesat a position for adjusting the shortest focal point are brought intoagreement at a focal distance, or to the positions in the vicinitiesthereof.

[0024] The invention further provides a stereo camera in which the lociof motion of the two photographing lenses are right-and-left symmetricalarcs passing through the positions at where the distance between theoptical axes of the two photographing lenses at a position for adjustingthe focal point to infinity is narrower than a pitch between the rightand left exposed pictures or, preferably, through the positions within arange of distance between the optical axes in which the visual fields ofthe two photographing lenses are brought into agreement at a distance of2 to 3 meters in front of the main points of the photographing lensesalong the optical axes, and through the positions of the distancebetween the optical axes at where the visual fields of the twophotographing lenses at a position for adjusting the shortest focalpoint are brought into agreement at a focal distance or through thepositions at where the distance between the optical axes is slightlynarrower than the distance between the optical axes with which thevisual fields are in agreement at the focal distance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a graph illustrating a straight locus of motion of aphotographing lens according to an embodiment of the present invention;

[0026]FIG. 2 is a graph illustrating a straight locus of motion of thephotographing lens according to the embodiment of the present invention;

[0027]FIG. 3 is a graph illustrating a permissible range for setting astraight locus of motion of the photographing lens according to theembodiment of the present invention;

[0028]FIG. 4 is a graph illustrating an arcuate locus of motion of thephotographing lens according to the embodiment of the present invention;

[0029]FIG. 5 is a graph illustrating a permissible range for setting thearcuate locus of motion of the photographing lens according to theembodiment of the present invention;

[0030]FIG. 6 is a graph illustrating the arcuate locus of motion of thephotographing lens according to the embodiment of the present invention;

[0031]FIG. 7 is a diagram illustrating a calculation for findingcoordinates of any lens position on an arc;

[0032]FIG. 8 is a table expressing the arcuate locus of motion of FIG. 6using numerical figures;

[0033]FIG. 9 is a diagram illustrating, in a disassembled manner, amechanism of the type of linear motion for automatically adjusting thedistance between the optical axes according to the embodiment of thepresent invention;

[0034]FIG. 10 is a sectional view of a stereo camera of the type oflinear motion;

[0035]FIG. 11 is a diagram illustrating the constitution of a finderportion of the stereo camera of FIG. 10;

[0036]FIG. 12 is a diagram illustrating the constitution of a mechanismfor automatically adjusting the distance between the optical axes in thestereo camera of FIG. 10;

[0037]FIG. 13 is a diagram illustrating the constitution of themechanism of the type of arcuate motion for automatically adjusting thedistance between the optical axes;

[0038]FIG. 14 is a vertical sectional view illustrating the structurefor coupling a lens board to the camera body of FIG. 13;

[0039]FIG. 15 is a sectional view of a stereo camera of the type ofarcuate motion;

[0040] FIGS. 16(L) and 16(R) are diagrams illustrating the constitutionsof parallel linking mechanisms in the stereo camera of FIG. 15;

[0041]FIG. 17 is a sectional view of the stereo camera of the type ofarcuate motion according to another embodiment;

[0042] FIGS. 18(L) and 18(R) are diagrams illustrating the constitutionsof parallel linking mechanisms in the stereo camera of FIG. 17;

[0043]FIG. 19 is a sectional view of the stereo camera of the type ofarcuate motion according to a further embodiment;

[0044] FIGS. 20(L) and 20(R) are diagrams illustrating filmsphotographed by using a conventional stereo camera;

[0045]FIG. 21 is a diagram illustrating losses of picture using theconventional stereo camera;

[0046]FIG. 22 is a diagram illustrating curved loci of motion of lenseswhen the visual fields of the right and left lenses are brought intoagreement at a focal distance; and

[0047]FIG. 23 is a table of numerical values representing distancesbetween the optical axes with which the visual fields of the right andleft photographing lenses are brought into agreement at the focaldistance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Embodiments of the present invention will now be described indetail. First, described below is a relationship between a distance atwhich the right and left windows of a stereo slide mount are broughtinto agreement to appear as a single window and a distance at which astereo image of a subject can be seen in viewing a stereo slide by usinga stereo slide viewer.

[0049] In a stereo slide photographed by using a conventional stereocamera of the type of automatically adjusting the distance between theoptical axes in which the visual fields of the right and left lenses arebrought into agreement at a focal distance, the visual fields of theright and left lenses are in agreement at the focal distance, and astereo image of a subject at the focal distance and the window of thestereo slide mount appear at an equal distance.

[0050] When, for example, a scenery at an infinity is photographed asshown in FIG. 22, the shifting amount Sl of the lens is zero.Accordingly, a pitch between the right and left pictures is equal to apitch of the same subject at infinity between the right and leftpictures, and the window of the stereo slide mount is seen at infinitylike the subject at infinity and the subject which is not at infinity isseen being located in front of the window of the stereo slide mount,which is unnatural. It is therefore presumed that a good result can beobtained if the photographing lenses are so shifted that the visualfields of the right and left photographing lenses are brought intoagreement at a distance shorter than the focal distance.

[0051] Therefore, considered below first is the shifting amount of thephotographing lenses of when the focal point is adjusted to infinity.

[0052] When,

[0053] focal distance of the photographing

[0054] lens f=36 mm,

[0055] pitch between the right and left

[0056] exposed pictures P=66 mm, and

[0057] pitch between the subjects at the

[0058] focal distance=Pi,

[0059] which are the conditions same as those of the prior art, a stereoimage of the subject at a distance of, for example, one meter and thewindow of the stereo slide mount can be seen at an equal distance whenthe shifting amount Sl of the photographing lenses is about 1.15 mm fromthe formula 2 when the focal point is adjusted to infinity. In thiscase, the images of the subjects at infinity move equally to theshifting amount of the photographing lenses on the exposed pictures ofthe films, i.e., respectively shifted by 1.15 mm in the directions inwhich they approach each other and, hence, the pitch Pi decreases by 2.3mm between the images of the subjects at infinity on the right and leftfilms. The image of the exposed picture of the stereo camera is aninverted image which is inverted right side left and upside down. Whenthe films photographed with the shifting amount Sl of 1.15 mm aremounted in a state of erect images on the stereo slide mount, the pitchPi between the subjects at infinity becomes larger by 2.3 mm than thepitch P (66 mm) between the right and left pictures.

[0060] When the pitch Pi between the subjects at the focal distance(infinity in this case) becomes very wider than the pitch P between theright and left pictures, the images will appear unnaturally as a matterof course. In order to examine the permissible range of expansion, theinventor has observed a variety of sample photographs varying theshifting amount of the photographing lenses. As a result, it wasevaluated that a difference between the pitch of the right and leftpictures and the pitch of the images of the same subject of the rightand left pictures, should not generally be larger than about 1.2 mm.

[0061] That is, when the shifting amount Sl of the right and leftphotographing lenses is not larger than 0.6 mm at the time ofphotographing a subject at infinity under the above-mentionedconditions, the difference between the pitch of the pictures and thepitch of the images of the same subject at infinity of the right andleft pictures becomes not larger than 1.2 mm, and the image at infinitydoes not appear unnaturally, and favorable three-dimensional feeling isobtained despite there exists an image of a subject at a short distancein the picture.

[0062] Though the shifting amount of the photographing lenses in thecase of infinity is set to be 0.6 mm, this value of 0.6 mm is nearlyequal to the shifting amount Sl with which the window of the stereoslide mount is seen at an equal distance as the subject of about 2meters as calculated from the formula 2.

[0063] Next, considered below is the shifting amount of thephotographing lenses in the case of the shortest focal distance. Even inthe case of the shortest focal distance, the condition is applied inthat the pitch between the images of the subject at a focal ditance iswider by about 1.2 mm than the pitch between the windows of the stereoslide mount like the case of photographing a subject at infinity. Thatis, when the shortest focal distance is L=360 mm,

Δif=f ²/(L−f)=36²/(360 −36)=4 mm

[0064] The moving amount Si of the image on either the right or leftpicture is 1.2/2=0.6 mm. In this case, the shifting amount Sl of thephotographing lenses is given by,

Sl=(P−(L×Pi)/(L+f+Δif))/2

=(P−(L×(P−1.2))/(L+f+Δif))/2

=(66−(360×(66 −1.2))/(360+36+4))/2

=3.84 mm

[0065] Furthermore, the distance Lw with which the visual fields of theright and left photographing lenses are brought into agreement, i.e.,the distance with which the right and left windows of the stereo slidemount appears as a single window, is given as follows:

Lw=(f+Δif)(P−2Sl)/2Sl=(36+4)(66−2×3.84)/2×3.84=304 mm

[0066]FIG. 1 shows the locus of motion of the left photographing lensonly, which is described by coupling a position of the lens at the timeof shooting a subject at infinity to a position of the lens at theshortest focal distance. The windows of the stereo slide mount are setat a distance of about 2 meters from the main points of thephotographing lenses when shooting the subject at infinity, and are setat positions of 304 mm in the case of the shortest focal distance of 360mm.

[0067] In the above-mentioned example, the shifting amount toward theinner side is larger than that of the locus L_(REF) represented by abroken line of the lenses of the conventional stereo camera of the typewhich automatically adjusts the distance between the optical axes overthe whole range for adjusting the focal point. Most of the photographedfilms can be mounted on the stereo slide mount without correcting thepositions for mounting the films or without masking portions of thepictures.

[0068] In FIG. 1, furthermore, the angle θ of inclination of the linearlocus relative to the optical axis is given by,

θ=tan⁻¹(3.84−0.6)/4=tan⁻¹ 0.81=39° 00′

[0069] and the shifting amount Sl of the lenses in the direction atright angles with the optical axis is given by,

Sl=0.6+Δif×tan θ (θ=39° 00′)

[0070] Here, the shifting amount Sl of the photographing lenses of whenthe focal point is brought to a distance of, for example, one meter, isfound to be,

Δif=f ²/(L−f)=36²/(1000−36)=1.344 mm

Sl=0.6+1.344×tan 39° 00′=1.688 mm

[0071] The moving amount of the image at infinity on the picture isequal to the shifting amount Sl of the photographing lens. Therefore,when the background at infinity is photographed on the picture in thecase when the focal point is adjusted to a distance of one meter, thepitch between the images of the background at infinity on the right andleft pictures is increased by about 3.4 mm (=2Sl) compared to the pitchbetween the pictures.

[0072] This is in excess of a recommended range (not larger than about1.2 mm) of the difference between the above-mentioned pitch of picturesand the pitch of images of the subject. It is therefore desired that thebackground at a distance does not enter as much as possible into thepicture when shooting a subject from a close distance.

[0073] The above-mentioned locus of motion of the lens is whenimportance is given to taking a picture from a close distance. However,users in general shoot the subjects at distances of not smaller than onemeter. Besides, many cameras have the shortest focal distance of aboutone meter. In these cases, the shifting amount may be decreased as awhole compared to the amount of FIG. 1 (at a position of adjusting thefocal point to infinity as shown, for example, in FIG. 2, the window ofthe stereo slide mount can be seen at 3 meters when the shifting amountis Sl=0.39 mm), or the angle of inclination of the locus of motion maybe decreased with respect to the optical axis of the photographing lens,in order to suppress the problem in that the pitch of image in thebackground becomes excessive when the subject at a short distance andthe background at a distance are photographed on the same picture.

[0074] Referring to FIG. 2, the locus of motion of the photographinglens intersects a conventional curved locus L_(REF) at a focal distanceof about 700 mm (Δif ≈2.0 mm). Except when shooting a subject from aclose distance, most of the films do not require correction at the timeof mounting. Only the films photographed from a close distance may becorrected for their mounting positions or may be masked for theirpictures as required.

[0075] Therefore, the loci of photographing lenses can be set within arange between the linear locus shown in FIG. 1 and the linear locusshown in FIG. 2 depending upon whether importance is given to shootingpictures from a close distance, importance is given to shooting picturesfrom general distances, or upon the conditions of the shortest focaldistance of the photographing lenses. When a locus is set in a rangebetween the two straight lines as shown in FIG. 3, there is obtained afavorable effect for correcting the distance between the optical axesbetter than that of the conventional stereo camera. Moreover, since thephotographing lenses are linearly moved, the structure of the mechanismfor adjusting the distance between the optical axes is simplified, and ahigh operation precision is accomplished.

[0076] In the foregoing was described the case where the photographinglenses were moved along the linear loci. Operation maintaining a highprecision can be further expected by using a mechanism for adjusting thedistance between the optical axes by moving the photographing lensesalong arcuate loci by using parallel linking mechanisms made up of acombination of a plurality of levers and links.

[0077] When the arcuate loci are employed, the radius is equal to, orlarger than, that of the conventional curved loci, the photographinglenses are inwardly shifted at a position for adjusting the focal pointto infinity, the shifting amount is decreased as the lenses aredelivered, and the distance of the window of the stereo slide mount isbrought nearly in agreement with a distance at which is seen a stereoimage of the focused subject at the shortest shooting distance. In thiscase, however, the arc has a large radius and the links becomes long.Therefore, the mechanism can be incorporated in a large camera butcannot be incorporated in a small camera.

[0078] The radii of arcs can be decreased if, as shown in FIG. 4, thephotographing lenses are moved along the arcs having centers of radii onthe center sides between the right and left photographing lensescontrary to that of the conventional curved locus L_(REF). The shiftingamount may be set within a range of from 0.39 to 0.6 mm so that thewindow of the stereo slide mount can be seen at a distance of about 2 to3 meters at a position for adjusting the focal point to infinity.Besides, at the shortest focal distance, the shifting position may beset within a relatively narrow permissible range inclusive of theshifting position of the conventional curved locus L_(REF). However, theposition may be set depending upon the conditions such as desiredshifting characteristics, focal distance of the lens, shortest focaldistance, etc., and no numerical limitation is imposed thereon like thatof the linear locus.

[0079] Therefore, a variety of arcs having different centers of arcs anddifferent radii of arcs can be set as represented by arcs A, B and C inFIG. 5. Like the range of linear loci shown in FIG. 3, however, the arcsare limited within a range which is not much displaced from theconventional curved locus L_(REF) as a matter of course.

[0080] In FIG. 5, the arc A represents the locus of motion of the lensof a stereo camera of claim 7, with which the window of the stereo slidemount appears at a distance of about 2 meters when the focal point isadjusted to infinity, a stereo image of a subject at a focal distance(e.g., 700 mm) appears at a distance equal to that of the window of thestereo slide mount at any intermediate position within a range foradjusting the focal point, and, on the side of short distances, thestereo image of the subject at the focal distance appears again at adistance equal to that of the window of the stereo slide mount at theshortest focal distance though the shifting amount becomes insufficient.

[0081] The arc B represents the locus of motion of the lens of a stereocamera of claim 8, with which the window of the stereo slide mountappears at a distance of about 2 meters when the focal point is adjustedto infinity, a stereo image of a subject at a focal distance appears ata distance equal to that of the window of the stereo slide mount at anintermediate position within a range for adjusting the focal point, and,on the side of short distances, the stereo image of the subject at thefocal distance appears at the back of the window of the stereo slidemount. The arc B has a radius smaller than that of the arc A, and makesit possible to shorten the length of the links.

[0082] The arc C represents the locus of motion of the lens of a stereocamera of claim 9. The center of radius of the arc B is shifted inward(toward the right in FIG. 5) to increase the shifting amount over thewhole areas so will not to come into contact with the conventionalcurved locus L_(REF).

[0083] Described below is a calculation for finding a locus of an arc Dshown in FIG. 6. When the focal distance of the lens is 36 mm, the pitchP₁, between the right and left exposed pictures is 66 mm, the distancewith which the visual fields of the right and left lenses come intoagreement is 2.5 meters when the focal point is adjusted to infinity,and the position of the lens is O′ like in the above-mentioned example,then, from the formula 2, the shifting amount of the point O′ is givenby,

Sl=(66/2)×36/(2500+36)=0.468 mm

[0084] and the distance Xo′ between the point O and the point O′ becomesabout 0.47 mm. Then, a point where an arc which is the locus of motionof the lens intersects the conventional curve represented by a brokenline is denoted by Q, a chord O′Q is drawn between O′ and Q of the arcand, similarly, a chord PQ is drawn between P and Q of the arc. Aperpendicular A is drawn from an intermediate point S of the chord O′Q,a perpendicular B is drawn from an intermediate point T of the chord PQ,and a point where the perpendiculars A and B meet together is found.This intersecting point is a center V of the arc O′QP.

[0085] The coordinate position of the point O′ is x=0.47, y=0. If Δif ofthe point Q is 2 mm which is an intermediate point of the range of 4 mmin which the lens moves in the direction of the optical axis, then, thex-coordinate of the point Q is x≈1.7368 and the y-coordinate is y=2 fromthe table of FIG. 23.

[0086] A difference in the x-value between the point O′ and the point Qis given by,

X _(Q) −X _(O)′=1.7368−0.47=1.2668

[0087] A difference in the y-value is,

y _(Q) −y _(O)′=2

[0088] The ratio of inclination of the chord O′Q relative to the opticalaxis is 1.2668/2=0.6334.

[0089] The coordinate position of the point S is,

x=(0.47+1.7368)/2=1.1034

y=2/2=1

[0090] The y-value on the perpendicular A when x=0 is,

y=1+1.1034×0.6334=1.69889356

[0091] and the numerical formula representing the perpendicular A isgiven by, y=−0.6334X+1.69889356

[0092] Similarly, a difference in the y-value between the point P andthe point Q on the perpendicular B is,

y _(Q) −y _(O)′=4−2=2

[0093] From FIG. 23, a difference in the x-value is,

X _(P) −X _(Q)=3.30−1.7368=1.5632

[0094] The ratio of inclination of the chord PQ relative to the opticalaxis is,

1.5632/2=0.7816

[0095] The coordinate position of the point T is,

x=(3.30+1.7368)/2=2.5184

y(4+2)/2=3

[0096] The y-value on the perpendicular B when x=0 is,

y=3+2.5184×0.7816=4.96838144

[0097] and the perpendicular B is expressed as,

y=−0.7816X+4.96838144

[0098] The coordinates are in agreement at a point where theperpendiculars A and B intersect and, hence,

−0.6334X+1.69889356=−0.7816X+4.96838144

[0099] Upon transposition,

−0.6334X+0.7816X=4.96838144−1.69889356

[0100] By rearranging both sides,

0.1482X=3.26948788

X=22.06132173

[0101] Furthermore,

y=−0.7816×22.0613+4.9683=−12.2748

X _(V)=22.0613 mm

Y _(V)=−12.2748 mm

[0102] Since the point O′ is positioned on the arc D, the radius R_(V)of the arc D is given by,

R _(V)={square root}{square root over ( )}((X _(V) −X _(O)′)² +Y _(V)²)={square root}{square root over ()}((22.0163−0.47)²+12.2748²)=24.83656 mm

[0103] From the radius R_(v) of the arc and the center coordinatesX_(V), Y_(V), furthermore, a lens position a on an arc shown in FIG. 7is,

βa=sin⁻¹((Δif−Y _(V))/R _(V))

Xa=X _(V) −R _(V) cos βa

[0104] Table of FIG. 8 shows calculated values of Δif of the arc D, Sl,βa and Xa.

[0105] In this example, the window of the stereo slide mount is set to2.5 meters when the focal point is adjusted to infinity. When the focalpoint is adjusted to about 700 mm, the window of the stereo slide mountappears at about 700 mm which is equal to the focal distance. When thefocal point is adjusted to a distance shorter than about 700 mm, thewindow of the stereo slide mount may appear slightly farther than thefocal distance. However, the difference is so small that the offsetneeds be corrected by a very small amount at the time of mounting. Whenthe arc data shown in the table of FIG. 8 are applied to a stereo cameraof which the shortest focal distance is larger than 700 mm, the optimumeffect for correcting the distance between the optical axes can beobtained under almost all conditions.

[0106] Next, concretely described below is the structure of themechanism for automatically adjusting the distance between the opticalaxes. FIG. 9 illustrates the mechanism for automatically adjusting thedistance between the optical axes by linearly moving the lens boards,wherein reference numeral 1 denotes a slide base, and 2L and 2R denotesliders, the sliders 2L, 2R and lens boards 3L, 3R at the front portionsthereof being coupled together as unitary structures. Right-and-leftsymmetrical linear tilted guide grooves 4L and 4R are formed in theupper surface of the slide base secured to the bottom part of the camerabody, and ribs 5L and 5R are formed on the lower surfaces of the sliders2L and 2R so as to be opposed to the guide grooves 4L and 4R.

[0107] Linear parallel grooves 6L and 6R are formed in the insideportions of the right and left sliders 2R, 2L, i.e., in the inner sidesof the optical axes of the right and left photographing lenses, thedirections of the parallel grooves 6L and 6R being at right angles withthe directions of the ribs 5L, 5R.

[0108] The upper half of the inner portion of the left slider 2L inwhich the parallel groove 6L is formed, is cut away so as to have athickness one-half the thickness of the slider 2L. The lower half of theinner portion of the right slider 2R is cut away, too, so as to have athickness one-half the thickness of the slider 2R. In a state where thesliders 2L and 2R are mounted on the slide base 1, the inner portions ofthe right and left sliders 2R and 2L are superposed one upon the other.

[0109] A bearing 8 of cams for moving the lenses is mounted on a centralbearing-mounting hole 1 a formed in the slide base 1. The cams 7L and 7Rare mounted in upper and lower two stages on an upper part of a shaftfor adjusting the focal point, and a pulley 9 is attached to a lowerpart of the shaft for adjusting the focal point.

[0110] The left cam 7L and the right cam 7R are circular eccentric camsof the same shape, have a diameter nearly equal to the width of theparallel grooves 6L, 6R in the sliders 2L, 2R, and are mounted on theshaft for adjusting the focal point maintaining a rotational angulardifference equal to an angle subtended by the right and left guidegrooves 4R, 4L, the left cam 7L engaging with the parallel groove 6L ofthe left slider 2L and the right cam 7R engaging with the parallelgroove 6R of the right slider 2R.

[0111] A knob 11 for adjusting the focal point is attached to the headof a pulley shaft 10 supported by a camera body (not shown), and a wire13 or a belt is wrapped round a pulley 12 attached to a lower part ofthe pulley shaft 10 and a pulley 9 of the shaft for adjusting the focalpoint.

[0112] When the knob 11 for adjusting the focal point is turned, thecams 7L and 7R are turned being interlocked to each other, the right andleft sliders 2R, 2L move aslant along the guide grooves 4L, 4R insynchronism with each other, and the distance between the optical axesis automatically adjusted being interlocked to the adjustment of thefocal point. As described above, the directions of the parallel grooves6L, 6R are at right angles with the directions of the guide grooves 4L,4R, and the directions in which the sliders 2L, 2R move are in agreementwith the directions in which the pushing forces of the cams 7L, 7R act.Therefore, the sliders 2L, 2R slide smoothly.

[0113] If the wire 13 wrapped round the pulleys 9 and 12 is secured at apoint on the circumferences of the pulleys 9 and 12, though thispertains to a widely known means, the wire 13 is prevented fromslipping, and the pair of pulleys 9 and 12 can be reliably rotated insynchronism.

[0114]FIG. 10 illustrates a three-lens type stereo camera 14 mounting amechanism for linearly adjusting the distance between the optical axesof FIG. 9, wherein a finder lens 16 is arranged at the center on thefront surface of a camera body 15, and a pair of photographing lenses17L, 17R are arranged on the right and left sides thereof in line in thelateral direction, and the optical axes of the three lenses 16, 17L and17R are in parallel and are positioned on the same plane. A focal planeshutter (not shown) is arranged at the back of the photographing lenses17L, 17R in just front of the exposed surfaces. Referring to FIG. 11, a45-degree reflex mirror 18 is secured at the back of the finder lens 16.Light falling on the finder lens 16 passes through the reflex mirror 18,focused on an upper focusing plate 19, and can be observed as an erectimage through a penta prism 20 and an eyepiece 21 in the same manner asthe general single-lens reflex camera.

[0115]FIG. 12 illustrates sliders 22 for mounting a finder lens board,and lens boards 3L, 3R for photographing lenses. The sliders 22 areprovided with a parallel groove 23 in the right-and-left direction, anda circular eccentric cam 24 for moving the finder lens is engaged withthe parallel groove 23, the circular eccentric cam 24 being provided onthe shaft for adjusting the focal point like the cams 7L, 7R for movingthe photographing lenses. Therefore, the three lenses 16, 17L and 17Rmove back and forth in synchronism being interlocked to the turn of theshaft for adjusting the focal point, and the state for adjusting thefocal point can be judged depending upon the state where the image isfocused on the focusing plate 19.

[0116] The finder lens 16 may have a focal distance equal to that of thephotographing lenses 17L, 17R. However, use of the finder lens having afocal distance shorter than that of the photographing lenses makes itpossible to decrease the space occupied by the finder portion. In thiscase, the size of the focusing plate 19 shown in FIG. 11 is decreased,the angle of image on the focusing plate is brought into agreement withthe angle of images exposed through the photographing lenses 17L, 17R.Besides, the shape and size of the cam 24 for moving the finder lens andthe width of the parallel groove 23 in the sliders 22, are so designedthat the moving amount of the finder lens satisfies the formulaΔif=f²/(L−f).

[0117]FIG. 13 illustrates a mechanism for adjusting the distance betweenthe optical axes being interlocked to the adjustment of the focal pointin the stereo camera in order to move the photographing lenses along anarcuate loci. Two right and left vertical shafts 32R and 32L arerotatably mounted on a body frame (not shown) of the stereo camera 31,and synchronizing gears 33L and 33R of the same shape are in mesh witheach other being mounted on the upper portions of the two verticalshafts 32L and 32R. A pinion gear 35, a cam 36 for moving a movablemirror of a range finder and a knob 37 for adjusting the focal point,are attached to a shaft 34 for adjusting the focal point disposed infront of the vertical shafts 32L, 32R, and a pinion gear 35 is broughtinto mesh with the one synchronizing gear 33R.

[0118] Bell crank-shaped levers 39 are secured to the upper and lowerportions of the vertical shafts 32L, 32R. Upper and lower two bellcrank-shaped levers 39 disposed on the outer sides of the verticalshafts 32L, 32R are supported by the upper and lower bearings of whichthe central shafts are provided on the body frame (not shown). The frontends of these right and left four levers 39 are pivoted near to theinner ends and the outer ends on both the upper and lower surfaces ofthe right and left lens boards 38R, 38L. Moreover, the rear ends of theopposing two levers are coupled together by links 40 to constituteparallel linking mechanisms.

[0119] The lever-pivoting points of the right and left lens boards 38R,38L are located on the outer sides of the vertical shafts 32L, 32R. Uponturning the knob 37 for adjusting the focal point, therefore, the rightand left lens boards 38R, 38L undergo a parallel motion on arcuate locimaintaining a right angled relationship with respect to the optical axesof the photographing lenses. Furthermore, the state of adjusting thefocal point can be viewed by turning the movable mirror of the rangefinder due to the cam 36 for the range finder. The structure of therange finder has been widely known and is not described here.

[0120]FIG. 14 illustrates the structure for mounting the lens boards38L, 38R on the camera body. The upper and lower both ends of the lensboards slide in contact with the upper and lower wall surfaces of thestereo camera 31 to interrupt light coming from the outside, andcorrectly maintain the positions of the lens boards 38L, 38R in theup-and-down direction. As means for shielding the gaps between the sidesurfaces of the lens boards and the camera body, furthermore, thin leafsprings that will be described later are attached to the camera body andare resiliently contacted to the side surfaces of the lens boardsthereby to shield the gaps between the lens boards and the camera body.

[0121] The radii of arcuate loci along which the lens boards 38L, 38Rmove are determined by distances between the lever-pivoting points ofthe lens boards 38L, 38R and the centers of the vertical shafts 32L, 32Rshown in FIG. 13. A variety of arcuate loci as shown in FIGS. 5 and 6can be realized depending upon the lengths of the levers and the centralpositions of the vertical shafts 32L, 32R.

[0122] The links 40 coupling the levers 39 may be omitted. When thelinks 40 are omitted, straight lines passing through the twolever-pivoting points on both the right and left sides of the lensboards 38L, 38R approach the vertical shafts 32L, 32R, and the operationmay lose smoothness when the dead points of the parallel linkingmechanisms are approached. Upon coupling the other ends of the bellcrank-shaped levers 39 with the links 40, however, the dead points canbe eliminated, and smooth operation is realized throughout the wholerange of motion.

[0123]FIG. 15 illustrates the stereo camera according to anotherembodiment. In this stereo camera 41, the right and left lens boards 42Rand 42L are driven in a synchronized manner through the cam 43, so thatthe photographing lenses 44L and 44R move along arcuate loci. As shownin FIGS. 16(L) and 16(R), straight parallel grooves 45R and 45L areformed in the inner portions of the right and left lens boards 42R, 42Lin a direction at right angles with the optical axes of thephotographing lenses 44R and 44L.

[0124] Like the lens boards 2L, 2R in FIG. 12, the upper half is cutaway from a portion forming a groove on the inner side of the left lensboard 42L so as to have a thickness one-half the thickness of the lensboard 42L. The upper half is cut away, too, from a portion forming agroove of the right lens board 42R so as to have a thickness one-halfthe thickness of the lens board 42R. The cut-away portions of the rightand left lens boards 42R and 42L are superposed one upon the other, andare coupled to the camera body 46 via two links 47 having an equallength.

[0125] A circular eccentric cam 43 disposed at the center of the baseframe 46 is inserted in the parallel grooves 45R, 45L of the right andleft lens boards 42R, 42L. Upon turning the shaft for adjusting thefocal point on which the cam 43 is mounted, the right and left lensboards 42R, 42L move symmetrically along the arcuate loci.

[0126] The side surfaces of the lens boards 42R, 42L are formed in anarcuate shape being curved in an opposing manner relative to the loci ofmotion, and the edges at the ends of the leaf springs 48 attached to thecamera body 46 are resiliently contacted to the side surfaces of thelens boards 42R, 42L. Therefore, no gap is formed between the leafsprings 48 and the lens boards 42R, 42L irrespective of the positions ofthe lens boards for adjusting the focal point, and the interior of thecamera body 46 is kept off from the infiltration of light, dust or waterdroplets.

[0127]FIGS. 17 and 18 illustrate another embodiment. In this stereocamera 61, the links have a length shorter than that of the stereocamera 41 of FIG. 14. The right and left two links 62 are pivoted attheir intermediate points, and the central two links 62 are rotatablymounted on the shaft 64 for adjusting the focal point.

[0128] A left lens board 65L is coupled to the front ends of the twolinks 62 constituting a parallel linking mechanism of the left side, aright lens board 65R is coupled to the front ends of the two links 62constituting a parallel linking mechanism of the right side, and theother ends of the two sets of links are coupled together by cam followerlinks 66L, 66R.

[0129] A circular eccentric cam 67 is engaged with parallel grooves 68L,68R of two pieces of cam follower links 66L, 66R that are superposed oneupon the other. When the cam 67 is turned, the right and left lensboards 65R and 65L move symmetrically describing arcs via the camfollower links 66L, 66R. The action is the same as that of FIG. 14.However, the radius of arcs is smaller since the levers are shorter thanthose of FIG. 14.

[0130] In a stereo camera 71 shown in FIG. 19, the front portions of theright and left two links 72 constituting a parallel linking mechanismare pivoted to the camera body 73, and the rear ends of the links 72 arepivoted to the rear portions of the lens boards 74L, 74R. The centers ofradii of loci along which the right and left lens boards 74R and 74Lmove are positioned on the outer sides of the optical axes; i.e., thearcuate loci are approximate to the curved loci of the conventionalmechanism for automatically adjusting the distance between the opticalaxes.

[0131] The applicant has proposed already a stereo camera forsynthesizing a finder picture by projecting, onto a focusing plate, theinner one-halves of an inverted image (the left one-half of the visualfield of the left photographing lens and the right one-half of thevisual field of the right photographing lens) that is incident throughthe two photographing lenses relying upon the combination of a reflexmirror and one or a plurality of prisms. In this stereo camera, theright and left one-halves of the image in the finder are brought closeto each other or are separated away from each other making it possibleto judge the focusing state depending upon the distance for adjustingthe focal point of the photographing lenses.

[0132] In the stereo camera equipped with the mechanism for adjustingthe distance between the axes, the right and left one-halves of theimage in the finder are brought close to each other or are separatedaway from each other even relying upon a change in the distance betweenthe optical axes of the photographing lenses and, hence, the findersystem must be equipped with means for correcting the pitch between theright and left one-halves of the image. To cope with this need, therehas been proposed a stereo camera equipped with a mechanism which makesit possible to correctly adjust the focal point by automaticallycorrecting the visual fields of the right and left finder systems bymoving part or whole of the composite prism back and forth beinginterlocked to a change in the distance between the optical axes.

[0133] When the above-mentioned prism finder is mounted on the stereocamera of the present invention, a cam for moving the prism is mountedon the shaft for adjusting the focal point like the circular eccentriccam 24 for moving the finder lens shown in FIG. 12, and part or whole ofthe prism is moved back and forth being interlocked to the adjustment ofthe focal point/distance between the optical axes, in order to correctthe pitch between the right and left one-halves of the image of thefinder system and to highly precisely adjust the focal point.

[0134] As described above, the present invention deals with a stereocamera in which the distance between the optical axes of thephotographing lenses is automatically adjusted depending upon thedistance of taking a picture, wherein the photographing lenses are movedalong the linear loci or arcuate loci corrected by taking the humanvisual sense into consideration. Therefore, the stereo camera is almostfree from unnatural perspective feeling that was often encountered withthe conventional stereo cameras. Thus, the stereo camera of theinvention enables everybody to easily shoot stereo pictures maintainingthe highest stereo effect, contributing to enhancing the practicabilityof the stereo camera.

[0135] The present invention is in no way limited to the above-mentionedembodiments only, but can be modified in a variety of ways withoutdeparting from the technical scope of the invention, and the inventionencompasses such modifications as a matter of course.

What is claimed is:
 1. A stereo camera provided with a mechanism for automatically adjusting the distance between the optical axes, in which two photographing lenses are mounted on independent lens boards, the distance between the right and left lens boards is changed being interlocked to the back-and-forth motion of the lens boards accompanying the operation for adjusting the focal point, and the distance between the optical axes of the two photographing lenses is corrected depending upon the focal distance, wherein the loci of motion of the two photographing lenses are right-and-left symmetrical straight lines connecting the positions at where the distance between the optical axes of the two photographing lenses at a position for adjusting the focal point to infinity is narrower than a pitch between the right and left exposed pictures or, preferably, connecting the positions within a range of distance between the optical axes in which the visual fields of the two photographing lenses are brought into agreement at a distance of 2 to 3 meters in front of the main points of the photographing lenses along the optical axes, to the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance, or to the positions in the vicinities thereof.
 2. A stereo camera according to claim 1 , wherein said loci of motion of the two photographing lenses are right-and-left symmetrical straight lines passing through the positions within a range of distances between the optical axes in which the visual fields of the two photographing lenses at a position for adjusting the focal point,to infinity are brought into agreement at a distance of 2 to 3 meters in front of the main points of the photographing lenses along the optical axes, and passing through the positions smaller than the distance between the optical axes with which the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance.
 3. A stereo camera according to claim 1 , wherein said loci of motion of the two photographing lenses are right-and-left symmetrical straight lines passing through the positions within a range of distances between the optical axes in which the visual fields of the two photographing lenses at a position for adjusting the focal point to infinity are brought into agreement at a distance of 2 to 3 meters in front of the main points of the photographing lenses along the optical axes, and passing through the positions of the distance between the optical axes with which the visual fields of the two photographing lenses are brought into agreement at a position for adjusting the focal point to a subject at a distance of about one meter.
 4. A stereo camera according to claim 1 , 2 or 3, wherein sliders having said two lens boards are mounted on a camera body via linear slide guide mechanisms, the inner portions of the two sliders are superposed one upon the other, parallel grooves are formed in the superposed portions being displaced by 90 degrees from the directions in which the sliders move, a perpendicular shaft for adjusting the focal point is disposed between the two sliders, two cams having the same shape are secured to said shaft for adjusting the focal point, said two cams have a fitting diameter nearly equal to the width of said parallel grooves and are secured with their relative rotational angles being so displaced as is equal to the angular displacement of the two sliders in the directions in which they move, the one cam is engaged with the parallel groove in the left slider, the other cam is engaged with the parallel groove in the right slider, and the two lens boards are right-and-left symmetrically moved back and forth in a tilted manner being interlocked to the turn of the shaft for adjusting the focal point.
 5. A stereo camera provided with a mechanism for automatically adjusting the distance between the optical axes, in which two photographing lenses are mounted on independent lens boards, the distance between the right and left lens boards is changed being interlocked to the back-and-forth motion of the lens boards accompanying the operation for adjusting the focal point, and the distance between the optical axes of the two photographing lenses is corrected depending upon the focal distance, wherein the loci of motion of the two photographing lenses are right-and-left symmetrical arcs passing through the positions at where the distance between the optical axes of the two photographing lenses at a position for adjusting the focal point to infinity is narrower than a pitch between the right and left exposed pictures or, preferably, through the positions within a range of distances between the optical axes in which the visual fields of the two photographing lenses are brought into agreement at a distance of 2 to 3 meters in front of the main points of the photographing lenses along the optical axes, and through the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance or through the positions at where the distance between the optical axes is slightly narrower than the distance between the optical axes with which the visual fields are brought into agreement at the focal distance.
 6. A stereo camera according to claim 5 , wherein the centers of radii of said arcuate loci of motion are located on the center side between the two photographing lenses.
 7. A stereo camera according to claim 6 , wherein the arcuate loci of motion of the two photographing lenses are right-and-left symmetrical arcs passing through the positions within a range of the distances between the optical axes in which the visual fields of the two photographing lenses at a position for adjusting the focal point to infinity are in agreement at a distance of 2 to 3 meters in front of the main points of the photographing lens along the optical axes, through the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the focal point to a subject at a distance of about one meter are in agreement at a focal distance, and through the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance.
 8. A stereo camera according to claim 6 , wherein the arcuate loci of motion of the two photographing lenses are right-and-left symmetrical arcs passing through the positions within a range of the distances between the optical axes in which the visual fields of the two photographing lenses at a position for adjusting the focal point to infinity are in agreement at a distance of 2 to 3 meters in front of the main points of the photographing lens along the optical axes, through the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the focal point to a subject at a distance of about one meter are in agreement at a focal distance, and through the positions at where the distance between the optical axes is slightly narrower than the distance between the optical axes with which the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance.
 9. A stereo camera according to claim 6 , wherein the arcuate loci of motion of the two photographing lenses are right-and-left symmetrical arcs passing through the positions within a range of the distances between the optical axes in which the visual fields of the two photographing lenses at a position for adjusting the focal point to infinity are in agreement at a distance of 2 to 3 meters in front of the main points of the photographing lenses along the optical axes, and through the positions of the distance between the optical axes slightly narrower than the positions of the distance between the optical axes at where the visual fields of the two photographing lenses at a position for adjusting the shortest focal point are brought into agreement at a focal distance, the distance between the optical axes being narrower than the distance between the optical axes in which the visual fields are in agreement at the focal distance throughout the whole range of adjusting the focal point.
 10. A stereo camera according to claim 5 , 6 , 7, 8 or 9, wherein the two lens boards are mounted on a camera body via a plurality of links to constitute two sets of parallel linking mechanisms, and the two lens boards and the two photographing lenses are moved along right-and-left symmetrical arcuate loci.
 11. A stereo camera according to claim 10 , wherein gears of the same shape are attached to the rotary shafts of said right and left two sets of parallel linking mechanisms, said two gears are brought into mesh with each other, and said right and left two sets of parallel linking mechanisms are operated in synchronism with each other.
 12. A stereo camera according to claim 10 , wherein the inner portions of the right and left lens boards mounted on said right and left two sets of parallel linking mechanisms are superposed one upon the others parallel grooves are formed in the superposed portions being displaced by nearly about 90 degrees with respect to the direction of the optical axes, a vertical shaft for adjusting the focal point is disposed between the two lens boards, a cam having a fitting diameter nearly equal to the width of said parallel grooves is secured to the shaft for adjusting the focal point, said cam is engaged with the parallel grooves formed in the right and left lens boards, and the shaft for adjusting the focal point is turned, so that the two lens boards move in synchronism along the arcs.
 13. A stereo camera according to claim 4 or 10 , wherein leaf springs are attached to the portions where the lens boards are mounted on the camera body of said stereo camera, and are resiliently contacted to the side surfaces of the right and left lens boards, in order to conceal the gaps between the camera body and the lens boards.
 14. A stereo camera according to claim 4 or 10 , wherein sliders mounting finder lenses are mounted to slide back and forth between the two lens boards, a cam for moving the sliders, which is a means for moving the sliders, is attached to the shaft for adjusting the focal point to move the lens boards, and an interlocking mechanism is constituted for adjusting the focal point/distance between the optical axes of the two lens boards and for adjusting the focal point of the finder lenses.
 15. A stereo camera according to claim 4 or 10 , wherein a prism-type finder is provided between said two lens boards to synthesize a finder picture by projecting, onto a focusing plate, a left one-half picture in the visual field of the left photographing lens and a right one-half picture in the visual field of the right photographing lens using a composite prism, said composite prism is partly or wholly mounted on the sliders to support it maintaining the freedom of sliding in the back-and-forth direction, a cam for moving the slider, which is a means for moving the sliders, is attached to the shaft for adjusting the focal point to move the lens boards, and an interlocking mechanism is constituted for adjusting the focal point/distance between the optical axes of the two lens boards and for correcting the visual field of the composite prism. 